WORCESTER — In the hours after Lee-Ann Rickheit made suicidal threats to her mother, police issued an Amber Alert for her 3-year-old daughter and tracked Rickheit’s phone to the Charlton area. Then, it powered off.

As the clock ticked, police raced from home to home, but found no trace of them. Then, they caught a break. A man who had seen Rickheit just hours before said she sometimes slept in her car behind Cook’s Pond.

Around 2:45 Thursday morning, police found the car parked in thick brush on the north side of the pond. Its lights were off, its windows fogged over.

Rickheit had blocked her tailpipe with clothes, allowing carbon monoxide fumes to fill the idling car for “a couple of hours’’ before they were found, she would later tell police. They had arrived just in time.

After smashing a side window, troopers awoke Rickheit and her daughter, covered with a blanket in the passenger’s seat. The child, who has been taken into state custody, is doing well, authorities said.

The details of the apparent murder-suicide attempt and dramatic rescue emerged Thursday as Rickheit, 38, was ordered held on $500,000 bail. She pleaded not guilty to attempted murder, reckless endangerment of a child, and assault and battery of a child.

After Rickheit was placed in custody, she told police she wanted to kill herself because “no one cares about me,’’ and that she didn’t “trust anyone one else’’ with her child, authorities said.

Rickheit has a lengthy criminal history and has struggled with mental illness, according to relatives and court records.

“My daughter loves her daughter very much, but she is mentally ill,’’ Rickheit’s mother, Dale Abbott, said Thursday. Abbott said her daughter has been diagnosed with bipolar disorder, depression, and anxiety. Rickheit sent her a text Wednesday stating that she was going to kill her daughter, prompting her to call the police, she said.

“My daughter tried to take my granddaughter’s life. . . . [Police] saved her in the nick of time,’’ she said. “I live for my grandkids.’’

Rickheit gave birth to her daughter while she was in jail, Abbott said. Abbott cared for the child at first, but Rickheit received custody in 2014 after attending a series of parenting classes while in jail, and after a period of weekend visitation, according to Abbott and court records.

Rickheit also has a 12-year-old son who lives with his father in Arlington, court records show. The father sought custody of the boy in 2008 after Rickheit was arrested twice. On two occasions, she had tried to kill herself, court documents show.

A number of complaints were filed against Rickheit for neglecting her son, according to court records. A social worker told the court that Rickheit abused alcohol and cocaine.

A relative who declined to provide her name questioned why Rickheit was granted custody of her daughter, given her troubles.

“She should not have had that kid,’’ the woman said.

A spokeswoman for the state Department of Children and Families declined to respond to questions about Rickheit’s fitness to care for the child, citing state and federal confidentiality laws and the pending criminal investigation.

On Thursday, the agency “took emergency custody of the child and is investigating in collaboration with law enforcement,’’ said spokeswoman Andrea Grossman.

Abbott said her granddaughter was placed in foster care. She said she has pleaded with child welfare officials to grant her custody, but was told her home was not large enough.

Another relative was denied because there is a dog in the home, she said.

“I told [my granddaughter] I’d be back,’’ Abbott said. “Now she’ll think I’m a liar.’’

Rickheit’s brother, Alan Abbott, said his sister’s troubles began in childhood.

“Obviously she’s dealing with some severe depression,’’ he said. “She’s been a person in the family with issues ever since we were kids. She’s always struggled with different things.’’

Rickheit was arrested in 2013 for pointing a replica gun at police, records show. After crashing her car into two other vehicles in Worcester, she fled on foot. When officers found her about 30 minutes later, she pulled out the replica and pointed it at them, telling officers it was real and threatening to shoot.

In 2008, she pleaded guilty to assault and battery and unarmed robbery for attacking a 66-year-old woman and snatching her purse, court records show. She was sentenced to 2½ years in jail and two years probation. That same year, she was charged with cocaine possession, according to news reports.

In 2009, Rickheit’s husband, Kurt Rickheit, a decorated military veteran, died from liver failure and pancreatic cancer, according to court documents.

A year later, a condo she shared with him fell into foreclosure.

Despite all her troubles, relatives said they never suspected Rickheit would try to hurt herself and her daughter.

“She feels like we all abandoned her,’’ said the relative, who declined to be identified. “I never thought she would take it this far. I never thought she would take her child.’’

John R. Ellement of Globe staff contributed to this report. Jan Ransom can be reached at jan.ransom@globe.com. Follow her on Twitter at @Jan_Ransom.